Automobile manufacturing utilizes multiple techniques for joining together multiple surfaces having relatively large cross sectional areas. In some instances, these surfaces have varying cross-sections or may be fabricated using materials of different thicknesses or shapes.
Some methods of joining these surfaces may utilize mechanical fasteners. However, mechanical fasteners may generate concerns over time allowing the surfaces to become disjoined. Another method of joining surfaces include welding using resistance, laser, plasma or seam welding techniques. In a typical welding application, plural surfaces are overlapped and mechanically fixed in place using clamps for example. A heat source, such as an electrode is placed near the overlapped surface and approaches the overlapped surfaces. As the heat source is position near the overlapped surfaces, the temperature of the region affected by the heat source quickly raises generally forming a liquid. The heat source then progresses along the overlapped surface until the desired weld is achieved. Upon completion of the weld, the heat source is removed from the surface, which is then cooled. In this way a weld joint may be created for joining two or more surfaces together. The traditional welding heat source presents several disadvantages including safety concerns related to the excess heat and inconsistent and incomplete welds. It would be beneficial, therefore, to provide an induction device, generating a thermal effect on the joined surfaces within a narrow zone to avoid any excess heat or unsafe working environments.
However, traditional welding techniques provide for irregular points of stress and require excess after-welding preparation to remove any unwanted edges or surfaces. Some welding techniques may not extend along the perimeter of the joined surfaces allowing for undesired Rat Holes. Others use a flanging or hemming operation to join the surface perimeters but allow for variations in the perimeter surfaces. However, these operations may require excess material which require additional time and resources for removal. Also, some welding techniques simply are too impractical or expensive for a manufacturing process which requires consistent movement along the manufacturing line.
Some of the aforementioned welding techniques may provide for one or more of the following problems like, “Rat Holes” or filiform corrosion due to the migration of water to the inner radius of a hemmed surface. Additionally, using the overlapping or seam welding process may allow for a hem flange which may require additional time and resources for removing any unwanted hems or seams. Some processes utilize an adhesive or temporary weld to temporarily secure the welded surfaces prior to being welding or during shipping and assembly operations. As a result of using the adhesive, a curing process may be necessary after the welding is accomplished and after which a sealant may be required. Using a temporary weld may further contribute to any delays or excess costs. These problems and excessive operations may contribute to delays and increased costs during the manufacturing process.
In addition to the concerns previously identified, the flanging, adhesive bonding and the hemming processes traditionally employed in the automobile manufacturing process may further present packaging limitations, which may be required to allow for an area to apply the adhesive, an area to hem the flange or an area to apply the hold-down fixture of the hemmer. It may be beneficial to remove the excess material, if an alternative welding process were utilized. Additionally, by removing any excess material an enhanced package design may be utilized for transporting the joined surfaces providing additional benefits. Utilizing an alternative welding process may also allow for improved stiffness and rigidity of the welded surface and allow for flanges having shorter dimensions.
Finally, by allowing for an improved welding process which provides for the joining of surfaces along a perimeter, the finished product may have improved characteristics through sharper radii such as reduced dimensional variation and enhanced design freedom. In addition, as previously described, utilizing an alternative welding process may render several manufacturing operations unnecessary, including the die flanging operation, the hemming operation, the application of hem adhesive, the need for after-hem sealer, induction curing of the hem adhesive and in-process welds for temporarily securing surfaces during transfer from the assembly process to the finishing processes.
It therefore would be beneficial to provide a superior quality, high productivity and economical welding apparatus which provides at least some of the aforementioned advantages, whereby materials with different thickness and/or different surfaces may be welded while shaping the joined surfaces.